The Importance of Diatoms

22 December 2010

The importance of diatoms as additional indicators for industry, mining and municipalities

Cyclotella meneghiniana

Diatoms are microscopic organisms, mostly less than ½ mm in length, which comprise approximately 40% of all algal assemblages. These organisms are important primary producers, providing both oxygen to the environment and a food source for primary and secondary consumers.

The diatoms are unique in that their cell wall is composed almost entirely of silica, thus they are extremely robust. Diatoms grow rapidly and communities can give an integrated overview of the prevailing water quality, for several weeks to months, on a small spatial scale. Diatoms persist in all habitats (rivers, streams, canals, ditches etc.), even in the most polluted, and are thus excellent universal indicators with well documented environmental tolerances.  They have proved extremely valuable for tracing the effects of acid mine drainage.

Over the past 9 years considerable effort has been made to establish these organisms as bioindicators in southern African waters, culminating in December 2010 with the production of the SA Diatom Index (SADI). This project, through its 3 phases, was lead by Dr. WR (Bill) Harding and funded by the Water Research Commission, with participation by the North-West University.

The project has shown that the collection and preservation of diatoms in both rapid and cost effective. Laboratory procedures and analysis are less than 3 hours per sample.

These unique organisms can now be used with confidence to inform both private and public enterprise on the following water quality issues:

  • Integrated water quality
  • Eutrophication or the addition of nutrients into the aquatic environment
  • Pollution by organic materials
  • Salinisation and the composition of dissolved salts
  • Changes in pH, including AMD
  • Presence of high concentrations toxic compounds (metals, pesticides etc.) – a Red Flag technique
  • Paleo-forensic determinations of historical water quality
  • Climate change trends

We are confident that these unique indicator organisms will provide a rapid and effective biomonitoring tool with universal application across southern Africa.  The lack of interest from the National Regulator, and the consequential termination of funding by the Water Research Commission (see Demise of the Diatom Project, 12 December 2010), has hamstrung further progress.

Bill Harding and Jonathan Taylor

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